Phylogeography of Phytophagous Weevils and Plant Species in Broadleaved Evergreen Forests: A Congruent Genetic Gap between Western and Eastern Parts of Japan.

Aoki K, Kato M, Murakami N - Insects (2011)

Bottom Line:
A comparison of the phylogeographic patterns of three types of phytophagous weevils associated with Castanopsis (a host-specific seed predator, a generalist seed predator, and a host-specific leaf miner) and several other plant species inhabiting the forests revealed largely congruent patterns of genetic differentiation between western and eastern parts of the main islands of Japan.Moreover, the congruent phylogeographic patterns observed in Castanopsis and the phytophagous insect species imply that the plant-herbivore relationship has been largely maintained since the last glacial periods.These results reinforce the robustness of the deduced glacial and postglacial histories of Castanopsis-associated organisms.

ABSTRACTThe Quaternary climate cycles played an important role in shaping the distribution of biodiversity among current populations, even in warm-temperate zones, where land was not covered by ice sheets. We focused on the Castanopsis-type broadleaved evergreen forest community in Japan, which characterizes the biodiversity and endemism of the warm-temperate zone. A comparison of the phylogeographic patterns of three types of phytophagous weevils associated with Castanopsis (a host-specific seed predator, a generalist seed predator, and a host-specific leaf miner) and several other plant species inhabiting the forests revealed largely congruent patterns of genetic differentiation between western and eastern parts of the main islands of Japan. A genetic gap was detected in the Kii Peninsula to Chugoku-Shikoku region, around the Seto Inland Sea. The patterns of western-eastern differentiation suggest past fragmentation of broadleaved evergreen forests into at least two separate refugia consisting of the southern parts of Kyushu to Shikoku and of Kii to Boso Peninsula. Moreover, the congruent phylogeographic patterns observed in Castanopsis and the phytophagous insect species imply that the plant-herbivore relationship has been largely maintained since the last glacial periods. These results reinforce the robustness of the deduced glacial and postglacial histories of Castanopsis-associated organisms.

f1-insects-02-00128: The location and vegetation of Japan. (a) The location of the Japanese Archipelago. The dotted line indicates the coastline of the Last Glacial Maximum about 20,000 years ago. (b) Vegetation during LGM based on Kamei and Research Group for the biogeography from Würm Glacial [29]. Circles indicate the existence of pollen records of broadleaved evergreen trees at the LGM [22,30]. (c) Potential natural vegetation at present [31].

Mentions:
Climatic changes during glacial periods have had a major influence on the recent evolutionary history of living organisms, even in the warm-temperate zone, where land was not covered by ice sheets [18,19]. The geological and geographical features of the Japanese Archipelago consist of several mountain ranges running parallel to a northeast-southwest-oriented axis. As the coastal belt is close to these mountain ranges, the climate varies even within a narrow region. Consequently, various types of vegetation occur in the archipelago (Figure 1a). Moreover, several landbridges between Japan and its surrounding areas, which formed or disappeared in response to glacial-interglacial climatic changes, have played important roles in determining the current distribution of the biological diversity in Japan [20]. Current warm-temperate and subtropical zones in the Japanese Archipelago are covered with forests mainly dominated by three types of broadleaved evergreen trees: Castanopsis, Quercus, and Machilus [21].

f1-insects-02-00128: The location and vegetation of Japan. (a) The location of the Japanese Archipelago. The dotted line indicates the coastline of the Last Glacial Maximum about 20,000 years ago. (b) Vegetation during LGM based on Kamei and Research Group for the biogeography from Würm Glacial [29]. Circles indicate the existence of pollen records of broadleaved evergreen trees at the LGM [22,30]. (c) Potential natural vegetation at present [31].

Mentions:
Climatic changes during glacial periods have had a major influence on the recent evolutionary history of living organisms, even in the warm-temperate zone, where land was not covered by ice sheets [18,19]. The geological and geographical features of the Japanese Archipelago consist of several mountain ranges running parallel to a northeast-southwest-oriented axis. As the coastal belt is close to these mountain ranges, the climate varies even within a narrow region. Consequently, various types of vegetation occur in the archipelago (Figure 1a). Moreover, several landbridges between Japan and its surrounding areas, which formed or disappeared in response to glacial-interglacial climatic changes, have played important roles in determining the current distribution of the biological diversity in Japan [20]. Current warm-temperate and subtropical zones in the Japanese Archipelago are covered with forests mainly dominated by three types of broadleaved evergreen trees: Castanopsis, Quercus, and Machilus [21].

Bottom Line:
A comparison of the phylogeographic patterns of three types of phytophagous weevils associated with Castanopsis (a host-specific seed predator, a generalist seed predator, and a host-specific leaf miner) and several other plant species inhabiting the forests revealed largely congruent patterns of genetic differentiation between western and eastern parts of the main islands of Japan.Moreover, the congruent phylogeographic patterns observed in Castanopsis and the phytophagous insect species imply that the plant-herbivore relationship has been largely maintained since the last glacial periods.These results reinforce the robustness of the deduced glacial and postglacial histories of Castanopsis-associated organisms.

ABSTRACTThe Quaternary climate cycles played an important role in shaping the distribution of biodiversity among current populations, even in warm-temperate zones, where land was not covered by ice sheets. We focused on the Castanopsis-type broadleaved evergreen forest community in Japan, which characterizes the biodiversity and endemism of the warm-temperate zone. A comparison of the phylogeographic patterns of three types of phytophagous weevils associated with Castanopsis (a host-specific seed predator, a generalist seed predator, and a host-specific leaf miner) and several other plant species inhabiting the forests revealed largely congruent patterns of genetic differentiation between western and eastern parts of the main islands of Japan. A genetic gap was detected in the Kii Peninsula to Chugoku-Shikoku region, around the Seto Inland Sea. The patterns of western-eastern differentiation suggest past fragmentation of broadleaved evergreen forests into at least two separate refugia consisting of the southern parts of Kyushu to Shikoku and of Kii to Boso Peninsula. Moreover, the congruent phylogeographic patterns observed in Castanopsis and the phytophagous insect species imply that the plant-herbivore relationship has been largely maintained since the last glacial periods. These results reinforce the robustness of the deduced glacial and postglacial histories of Castanopsis-associated organisms.